I hate to write this, but you probably know the unwritten rule is for a TKD BB to split, so that has to come before any other conditioning. Nevertheless, the general concept is to train for the intensity and duration of a match. Get a stopwatch and time the action of an international match; you will probably find it's at most half the round. You probably know the rest; paddles, shields, bag, jump-rope, and don't exercise sitting or laying down. Do as much as you can on one leg.
Do 50 of every strike you know every day and stretch like a fiend. Also fighting wing chun practitioners on the weeked is good for the soul.